"'Can't Help Falling in Love'is a song originally recorded by Elvis Presley and featured in the 1961 film, Blue Hawaii. It was written by Hugo Peretti, Luigi Creatore and George David Weiss.
The melody is based on "Plaisir d'amour" (1784), a popular romance by Jean Paul Egide Martini (1741?1816). "Plaisir d'amour" is a classical French love song written in 1784 by Jean-Paul-Égide Martini (1741?1816); it took its text from a poem by Jean-Pierre Claris de Florian (1755?1794), which appears in his novel Célestine. Hector Berlioz arranged it for orchestra (H134) in 1859."
I've heard that for years, but really the only overlap in melody between those two songs is one single line: "Chagrin d'amour dure la vie" and "For I can't help falling in love with you." And those two melody lines are far from identical anyway.